Wire network for interconnecting photovoltaic cells

ABSTRACT

Provided are novel interconnect wire network assemblies and methods of fabricating thereof. An assembly may include conductive portions/individual wires that, in certain embodiments, are substantially parallel to each other. The assembly also includes two or more carrier films (i.e., the front side and back side films) attached to opposite sides of the wires. The films are typically attached along the wire ends. The films are made from electrically insulating materials and at least the front side film is substantially transparent. The front side film is used to attach the wires to a photovoltaic surface of one cell, while the back side film is used for attachment to a substrate surface of another cell. These attachments electrically interconnect the two cells in series. In certain embodiments, one or both carrier films extend beyond two end wires and form insulated portions that allow much closer arrangements of the cells in a module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/822,712, titled “WIRE NETWORK FORINTERCONNECTING PHOTOVOLTAIC CELLS” filed on Aug. 10, 2015, which is adivisional of U.S. patent application Ser. No. 13/087,724 (nowabandoned), titled “WIRE NETWORK FOR INTERCONNECTING PHOTOVOLTAICCELLS,” filed Apr. 15, 2011, which is a continuation-in-part of U.S.patent application Ser. No. 12/566,555 (now abandoned), titled“INTERCONNECT ASSEMBLY,” filed Sep. 24, 2009, which is acontinuation-in-part of U.S. patent application Ser. No. 12/052,476(issued as U.S. Pat. No. 8,912,429), titled “INTERCONNECT ASSEMBLY,”filed Mar. 20, 2008, each of which is incorporated herein by referencein its entirety and for all purposes.

BACKGROUND

In the drive for renewable sources of energy, photovoltaic technologyhas assumed a preeminent position as a cheap and renewable source ofclean energy. For example, photovoltaic cells using a Copper IndiumGallium Diselenide (CIGS) absorber layer offer great promise forthin-film photovoltaic cells having high efficiency and low cost. Ofcomparable importance to the technology used to fabricate thin-filmcells themselves is the technology used to collect electrical currentfrom the cells and to interconnect one photovoltaic cell to another toform a photovoltaic module.

Just as the efficiency of thin-film photovoltaic cells is affected byparasitic series resistances, photovoltaic modules fabricated frommultiple cells are also impacted by parasitic series resistances andother factors caused by electrical connections to the absorber layer andother electrical connections within the modules. A significant challengeis the development of current collection and interconnection structuresthat improve overall performance of the module. Moreover, thereliability of photovoltaic modules is equally important as itdetermines their useful life, cost effectiveness, and viability asreliable alternative sources of energy.

SUMMARY

Provided are novel interconnect wire network assemblies and methods offabricating thereof. An assembly may include conductiveportions/individual wires that, in certain embodiments, aresubstantially parallel to each other. The assembly also includes two ormore carrier films (i.e., the front side and back side films) attachedto opposite sides of the wires. The films are typically attached alongthe wire ends. The films are made from electrically insulating materialsand at least the front side film is substantially transparent. The frontside film is used to attach the wires to a photovoltaic surface of onecell, while the back side film is used for attachment to a substratesurface of another cell. These attachments electrically interconnect thetwo cells in series. In certain embodiments, one or both carrier filmsextend beyond two end wires and form insulated portions that allow muchcloser arrangements of the cells in a module.

In certain embodiments, an interconnect wire network assembly includes aplurality of conductive portions extending substantially parallel toeach other, a first carrier film having a first substantiallytransparent electrically insulating layer, and a second carrier filmhaving a second substantially transparent electrically insulating layer.The plurality of conductive portions having a first set of ends defininga first edge and a second set of ends defining a second edge. Theplurality of conductive portions is configured for current collectionfrom a front side surface of a first photovoltaic cell and electricalconnection with a back side surface of a second photovoltaic cell. Thefirst carrier film is coupled to the plurality of conductive portionsalong the first edge and configured to attach the plurality ofconductive portions to the front side surface of the first photovoltaiccell to form a first electrical connection between the front sidesurface and the plurality of conductive portions. The second carrierfilm is coupled to the plurality of conductive portions along the secondedge and configured to attach the plurality of conductive portions tothe back side surface of the second photovoltaic cell to form a secondelectrical connection between the back side surface and the plurality ofconductive portions.

In certain embodiments, a first carrier film is positioned on anotherside of the conductive portions with respect to the second carrier film.The two films may overlap. In other embodiments, the two films may bepositioned at a predetermined distance from the second carrier film. Anoutside edge of the first carrier film may substantially coincide withthe first edge of the plurality of conductive portions. In otherembodiments, the first carrier film extends past the first edge of theconductive portions. In certain embodiments, conductive portions extendpast two edges of the first carrier film.

One or both carrier films may be made from one or more of the followingmaterials: polyethylene terephthalate, polyethylene co-methacrylic acid,polyamide, and polyetheretherketone. In the same or other embodiments,conductive portions may be made from one or more of the followingmaterials: copper, aluminum, nickel, and chrome. Conductive portions mayinclude multiple individual wires. These individual wires may be between24 gauge and 56 gauge. The individual wires may be spaced apart bybetween about 2 millimeters and about 5 millimeters. Each wire may beelectrically insulated from other wires prior to attaching theinterconnect wire network assembly to the first photovoltaic cell or thesecond photovoltaic cell. In certain embodiments, multiple individualwires have a strip of foil attached to the second edge and electricallyinterconnecting the multiple individual wires.

In certain embodiments, the first carrier film extends past two endwires of the plurality of conductive portions forming two sideinsulating regions. The first carrier film may extend past and foldsover two end conductive portions of the plurality of conductiveportions, forming insulating shells around the two end conductiveportions.

Provided also a method of fabricating an interconnect wire networkassembly. The method involves unwinding multiple individual wires fromcorresponding multiple wire rolls, extending the wires along anunwinding direction substantially parallel to each other at apredetermined distance from each other, applying a first carrier filmonto the first surface of the wires, and applying a second carrier filmonto the second surface of the wires. The two first carrier films may beapplied substantially perpendicular to the unwinding direction. Applyingthe first carrier film may involve passing an electric current through aportion of the multiple individual wires that is in contact with thefirst carrier film in order to heat this portion.

The method may also involve forming a roll of interconnect wire networksubassemblies, unwinding the roll of interconnect wire networksubassemblies, and cutting the multiple individual wires substantiallyperpendicular to the multiple individual wires to form the interconnectwire network assembly. In certain embodiments, the method involvescutting the multiple individual wires substantially perpendicular to themultiple individual wires to form the interconnect wire networkassembly. Such cutting may also involve cutting the first carrier filmor the second carrier film.

Provided also a photovoltaic module that includes a first photovoltaiccell having a front side surface, a second photovoltaic cell having aback side surface, and an interconnect wire network assembly. Theassembly may include a plurality of conductive portions extendingsubstantially parallel to each other and in electrical communicationwith the front side of the first photovoltaic cell and the back side ofthe second photovoltaic cell. The assembly also includes a first carrierfilm coupled to the plurality of conductive portions along the firstedge and attaching the plurality of conductive portions to the frontside surface of the first photovoltaic cell. Furthermore, the assemblyincludes a second carrier film coupled to the plurality of conductiveportions along the second edge and attaching the plurality of conductiveportions to the back side surface of the second photovoltaic cell. Theconductive portions include a first set of ends defining the first edgeand a second set of ends defining the second edge. The first carrierfilm is made from a first substantially transparent electricallyinsulating layer, while the second carrier film is made from a secondsubstantially transparent electrically insulating layer.

These and other embodiments are described further below with referenceto the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a photovoltaic module havingmultiple photovoltaic cells electrically interconnected with each otherusing interconnect wire network assemblies, in accordance with certainembodiments.

FIG. 2 is a schematic top view of an interconnect wire network assembly,in accordance with certain embodiments.

FIG. 3A is a schematic side view of an interconnect wire networkassembly depicted in FIG. 2, in accordance with certain embodiments.

FIG. 3B is a schematic side view of another interconnect wire networkassembly, in accordance with different embodiments.

FIG. 3C is a schematic side view of yet another interconnect wirenetwork assembly, in accordance with different embodiments.

FIG. 4 illustrates a process flowchart corresponding to a method offabricating an interconnect wire network assembly, in accordance withcertain embodiments.

FIG. 5 illustrates a schematic view of an apparatus for fabricating aninterconnect wire network assembly, in accordance with certainembodiments.

FIG. 6A is a schematic representation of a technique for cutting asubassembly to form an interconnect wire network assembly, in accordancewith certain embodiments.

FIG. 6B is a schematic representation of another technique for cutting asubassembly to form an interconnect wire network assembly, in accordancewith different embodiments.

FIG. 7 illustrates a schematic side view of two photovoltaic cellselectrically interconnected using an interconnect wire network assembly,in accordance with certain embodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Thepresent invention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail so as to not unnecessarily obscure the presentinvention. While the invention will be described in conjunction with thespecific embodiments, it will be understood that it is not intended tolimit the invention to the embodiments.

To provide a better understanding and context for the description ofvarious features of interconnect wire network assemblies, an example ofa photovoltaic module will now be described. FIG. 1 is a schematicrepresentation of a photovoltaic module 100 having multiple photovoltaiccells 104, in accordance with certain embodiments. Photovoltaic cells104 are electrically interconnected in series using multipleinterconnect wire network assemblies 106. Specifically, each pair ofcells 104 is interconnected using one assembly 106. FIG. 1 shows eightphotovoltaic cells interconnected with seven assemblies; however, itwill be understood that any number of cells may be used in a module. Incertain embodiments, a module includes at least 10 cells or, morespecifically, at least 15 cells interconnected in series. In particularembodiments, a module includes 22 cells interconnected in series.Furthermore, one set of cells interconnected using wire networkassemblies may be further connected to one or more similar sets in thesame module. For example, a module may include two sets, each setincluding 22 interconnected cells. The connections between the sets maybe provided by wire network assemblies or other components.

Multiple cells may be interconnected in series when individual cells donot provide an adequate output voltage. The output voltage requirementmay be driven by electrical current transmission and other factors. Forexample, a typical voltage output of an individual CIGS cell is between0.4V and 0.7V. A module built from CIGS cells is often designed toprovide a voltage output of at least about 20V or even higher. Inaddition to interconnecting multiple cells in series, a module mayinclude one or more module-integrated inverters. Interconnect wirenetwork assemblies 106 may be also used to provide uniform currentdistribution and collection from one or both contact layers, as furtherexplained below. It should be understood that these assemblies may alsobe used to provide parallel electrical connections or a combination ofin-series and parallel connections.

As shown in FIG. 1, each interconnect wire network assembly 106 (withthe exception of the bottom assembly, which is further described above)extends over a front side of one cell and under a back side of anothercell. One or both cells in this pair may be connected to other cells andso on. As such, most cells may have one interconnect wire networkassembly extending over its front side and another interconnect wirenetwork assembly extending under its back side. An end cell in the set(e.g., the top-most cell in FIG. 1) may have only one interconnect wirenetwork assembly extending over one of its surfaces, typically over thefront side. In this embodiment, a bus bar 108 may be connected directlyto the cell (i.e., to its back side). In some embodiments, an end cell(e.g., the bottom-most cell in FIG. 1) may still have two interconnectwire network assemblies. A bus bar 110 may be attached to one of theseassemblies. Specifically, bus bar 110 may be attached to a portion ofthe interconnect wire network assembly extending outside of the cellperimeter. Such attachment may involve welding, soldering, and otherforms of attachments, which are generally not suitable for attachmentdirectly to the cells.

When an interconnect wire network assembly extends over a front side ofthe photovoltaic cell, it makes an electrical connection with that sideor, more specifically, with a top layer arranged on that side. Incertain embodiments, a photovoltaic cell includes one or moretransparent conductive oxides (TCO), such as zinc oxide, aluminum-dopedzinc oxide (AZO), indium tin oxide (ITO), and gallium doped zinc oxide,disposed over the front side of the photovoltaic cell. A typicalthickness of a top conductive layer is between about 100 nanometers to1,000 nanometers (for example between about 200 nanometers and 800nanometers), with other thicknesses within the scope. The TCO providesan electrical connection between the entire photovoltaic layer and aportion of the interconnect wire network assembly extending over thefront side of the cell. Due to the limited conductivity of the TCOlayer, the interconnect wire network assembly typically extendsuniformly over the entire front side surface of the cell and providesuniform current distribution and collection from this surface. As such,an interconnect wire network assembly is sometimes referred to as acurrent collector. Various characteristics of interconnect wire networkassemblies allowing uniform current distribution and collection aredescribed below in the context of FIG. 2.

An interconnect wire network assembly extending under a back side of thecell makes an electrical connection with that side or more specificallywith a conductive substrate supporting the photovoltaic stack. Someexamples of photovoltaic stacks include CIGS cells, cadmium-telluride(Cd—Te) cells, amorphous silicon (a-Si) cells, micro-crystalline siliconcells, crystalline silicon (c-Si) cells, gallium arsenide multi-junctioncells, light adsorbing dye cells, and organic polymer cells. Someexamples of conductive substrates include stainless steel foil, titaniumfoil, copper foil, aluminum foil, beryllium foil, a conductive oxidedeposited over a polymer film (e.g., polyamide), a metal layer depositedover a polymer film, and other conductive structures and materials. Incertain embodiments, a conductive substrate has a thickness of betweenabout 2 mils and 50 mils (e.g., about 10 mils), with other thicknessesalso within the scope. Generally, a substrate is sufficiently conductivesuch that a uniform and extensive distribution of interconnect wirenetwork assembly wires is not needed for uniform current collection onthis side. As such, a portion of the wire network assembly extendingunder the back side of one cell may be smaller than a correspondingportion extending over a front side of an adjacent cell.

As shown in FIG. 1 and further explained below with reference to FIG. 2,interconnect wire network assemblies may include conductive portions,such as multiple individual wires, extending substantially parallel toeach other. When installed into the module, conductive portions extendunder photovoltaic cells and are illustrated with dashed line in FIG. 1.The other part of the conductive portions extends over front sides ofadjacent cells and is shown with solid lines. When cells are spacedapart as shown in FIG. 1, a part of the conductive portions extendsbetween the cells. In other embodiments, cells in the module may beadjacent to each other (e.g., have a minimal or no gap) or even overlap(sometimes referred to as a “shingle” arrangement). Interconnect wirenetwork assemblies also have insulating carrier films, which allowvarious insulation schemes that in turn allow these various cellarrangements, as will be now described in more detail.

FIG. 2 is a schematic top view of an interconnect wire network assembly200, in accordance with certain embodiments. Assembly 200 includesconductive portions 202 and two carrier films (i.e., a first carrierfilm 204 and a second carrier film 206). Since these films 204, 206 arecut to a predetermined length, these films 204, 206 may be also referredto as carrier strips or decals. A portion of conductive portions 202extends under first carrier film 204 from the top view perspectivepresented in FIG. 2. As such, this portion is shown with dashed lines.In certain embodiments, conductive portions 202 include multipleindividual wires continuously extending between two edges (i.e., thefirst edge and the second edge) defined by ends of the wires alongdirection X. In certain embodiments, these wires extend substantiallyparallel to each other. Specifically, an angle between any pair ofadjacent wires may be less than about 5° or, more specifically, lessthan about 1°. However, wires may extend in other directions and/orcross-over.

Substantially parallel wires are shown in FIG. 2 and may be arranged andspaced apart along the length of assembly 200, or direction Y. Thisarrangement may be characterized by a pitch 209, which, for purposes ofthis document, is defined as a distance between the centers of twoadjacent wires. The pitch determines the distance an electrical currenttravels through the conductive top layer of the cell prior to reachingmore conductive wires of the interconnect wire network assembly 200.Reducing the pitch increases the current collection characteristics ofassembly 200. However, a smaller pitch also decreases the useful surfacearea of the cell by covering the photovoltaic layer with non-transparentwires. In certain embodiments, pitch 209 is between about 2 millimetersand 5 millimeters (e.g., about 3.25 millimeters), although otherdistances may be used, as appropriate.

Conductive portions 202 are typically made from thin, highly conductivemetal stock and may have round, flat, and other shapes. As mentionedabove, conductive portions 202 are generally more conductive than theTCO layer and are used to improve current collection from the frontsurface of the cell. Examples of wire materials include copper,aluminum, nickel, chrome, or alloys thereof. In some embodiments, anickel coated copper wire is used. In certain embodiments, the wire is24 to 56 gauge, or in particular embodiments, 32 to 56 gauge (forexample, 40 to 50 gauge). In specific embodiments, the wire has a gaugeof 34, 36, 40, 42, 44, or 46. Additional wire examples are described inU.S. patent application Ser. No. 12/843,648, entitled “TEMPERATURERESISTANT CURRENT COLLECTORS FOR THIN FILM PHOTOVOLTAIC CELLS,” filedJul. 26, 2010, (Attorney Docket MSOLP039/IDF156), which is incorporatedherein by reference in its entirety for purposes of describingadditional wire examples.

Carrier films 204 and 206 are coupled to conductive portions 202 alongtwo edges defined by the ends of conductive portions 202, such as endsof wires shown in FIG. 2. These edges extend along the length of theassembly in direction Y and may be generally parallel to each other.Various positions of carrier films 204 and 206 with respect to theseedges are explained below with reference to FIGS. 3A, 3B, and 3C. Asnoted, during fabrication of a module, one carrier film is configured toattach wires 202 to a photovoltaic surface of one photovoltaic cell andmay be referred to as a top carrier film or a top decal. Another carrierfilm is configured to attach wires 202 to a substrate surface of anotherphotovoltaic cell and may be referred to as a bottom carrier film or abottom decal. Either one of carrier films 204 and 206 can be a topcarrier film, while another one can be a bottom carrier film. Thesedesignations are explained in more detail with reference to FIG. 7,which shows two photovoltaic cells interconnected using an interconnectwire network assembly. The attachments provided by the carrier filmsform electrical connections between conductive portions 202 and thephotovoltaic and substrate surfaces of two cells.

Both top and bottom carrier films are made from electrically insulatingmaterials. The top carrier film should also be substantially transparentso as to allow the sunlight to reach the photovoltaic layer. In certainembodiments, both carrier films are substantially transparentelectrically insulating layers. Some examples of suitable carrier filmmaterials include thermoplastic materials, such as polyethyleneterephthalate (PET), ionomer resins (e.g., poly(ethylene-co-methacrylicacid)), polyamide, polyetheretherketone (PEEK), or combinations ofthese. One particular example is SURLYN®, available from E. I. du Pontde Nemours and Company in Wilmington, Del. In certain embodiments, oneor both carrier films have a layered structure. For example, a carrierfilm may have three polymers layers, such as a co-extruded stackcontaining SURLYN®, PET, and another layer of SURLYN® (with the PETlayer positioned in between the two SURLYN® layers). In certainembodiments, a suitable carrier may be a thermoplastic material ormaterials curable using ultra violet (UV) or other techniques.

FIG. 3A is a schematic side view of the interconnect wire networkassembly 200 depicted in FIG. 2, in accordance with certain embodiments.This side view further illustrates various arrangements of the assemblythat may not be easily appreciated from the top view in FIG. 2.Specifically, FIG. 3A shows carrier films 204 and 206 attached toopposite sides of conductive portions 202. With reference to directionZ, carrier film 204 is positioned on the top side of conductive portions202, while carrier film 206 is positioned on the bottom side ofconductive portions 202. This orientation does not necessarilycorrespond to carrier film 204 being a top carrier film in the moduleassembly. In this orientation and reference, the bottom surface ofcarrier film 204 may be an adhesive surface and used for securingcarrier film 204 to conductive portions 202. Furthermore, the sameadhesive surface is used to secure carrier film 204 to the cell (e.g.,to a photovoltaic surface if carrier film 204 is a top carrier film)after integration of assembly 200 into the module. Correspondingly,carrier film 206 has a top adhesive surface for securing carrier film206 to conductive portions 202 and, after installation, to the cell(e.g., to a substrate surface if carrier film 206 is a bottom carrierfilm). Adhesion between the carrier films and conductive portions,during fabrication of the assembly, may be achieved by applying pressurebetween these components and/or heat to one or both components. Thesefeatures are further described below with reference to FIG. 4.

FIG. 3A illustrates carrier films 204 and 206 forming an overlap 208 inthe middle portion of assembly 200. This overlap may be used, in part,to prevent electrical shorts in the assembled module and for otherpurposes. At overlap 208, carrier films 204 and 206 may be adhered toeach other in the areas between adjacent conductive portions and outsideof end conductive portions to provide additional structural integrity toassembly 200. Further, conductive portions 202 are shown to extend pastthe outside edges of carrier films 204 and 206 (in direction X) and haveexposed ends 205 and 207.

Other arrangements of wires and carrier films in interconnect wirenetwork assemblies are possible. FIG. 3B is a schematic side view ofanother assembly 300, in accordance with different embodiments. Carrierfilms 304 and 306 extend past the wire ends (in direction X) and forminsulating regions or flaps 305 and 307. There may be a need to protectthe ends of the wires to prevent their sharp corners from causingelectrical shorts. Furthermore, carrier films 304 and 306 do not overlapin the middle portion of assembly 300. Instead carrier films 304 and 306form a gap 308 in that portion and expose a portion of wires 302. Thisgap 308 may help to improve the flexibility of assembly 300 around thisportion and may reduce the overall thickness of assembly 300.

FIG. 3C is a schematic side view of interconnect wire network assembly310, in accordance with different embodiments. Outside edges of carrierfilms 314 and 316 of this assembly coincide with the ends of wires 312.This type of arrangement may be formed by cutting wires 312 togetherwith carrier films 314 and 316 during fabrication of the assembly, asdescribed below with reference to FIG. 6B. Furthermore, carrier films314 and 316 do not overlap in the middle portion of the assembly.Instead, the inside edges of carrier films 314 and 316 coincide.

In general, respective positions of the carrier films' outside edgesrelative to the wires' ends are independent from respective positions ofthe inside edges. Various combinations of these respective positions arenot limited to the examples presented in FIGS. 3A, 3B, and 3C anddescribed above. Other combinations are possible (e.g., extended outsideedges (as shown in FIG. 3B) combined with overlapped inner edges (asshown in FIG. 3A), a middle gap (as shown in FIG. 3B) combined withexposed wire ends (as shown in FIG. 3A), and so on).

Returning to FIG. 2, carrier films 204 and 206 are shown to extendbeyond end wires 202 a and 202 b in Y direction. These extensions formtwo side insulating regions 211 a and 211 b, which may be referred to asinsulating flaps. Insulating regions 211 a and 211 b do not have anyconductive materials and may include only one or both carrier films. Assuch, insulating regions 211 a and 211 b can be used to insulate theedges of corresponding photovoltaic cells after fabrication of themodule. For example, this insulation allows a closer arrangement ofcells within a module along Y direction. It should be noted that onlyone carrier film may extend beyond end wires 202 a and 202 b to forminsulating regions 211 a and 211 b. In certain embodiments, there is notgap between two adjacent cells (not accounting portions of theinterconnect assemblies attached to these cells) in this direction. Thecells may even overlap in certain embodiments. Carrier films of theinterconnect assemblies may be used to insulate edges of the twoadjacent cells. For example, one portion of the carrier film may beattached to the front light incident side of the first cell, whileanother portion may extend outside of the first cell boundary and underthe back side of the adjacent cell. This extension insulated the twoadjacent edges of the cells with respect to each other.

In certain embodiments, conductive portions include individual wiressuch that each wire is electrically insulated from other wires. Forexample, the wires may extend substantially parallel to each otherand/or do not touch each other. One having ordinary skills in the artwould understand that such wires remain electrically insulated onlyuntil attachment of the assembly to a photovoltaic cell, during whichthe wires become interconnected by a front side, back side, or both. Inother embodiments, wires may be interconnected by a strip of foil orother wires. The interconnection may be provided along one set of wires'ends, similar to an example presented in FIG. 1. The interconnectingelement (e.g., a foil strip) may then be used for connection to bus barsand/or other electrical components of the module. In certainembodiments, an interconnecting element may be used to enhance anelectrical connection to a back side of the photovoltaic module.

FIG. 4 illustrates a flowchart corresponding to a process 400 offabricating an interconnect wire network assembly, in accordance withcertain embodiments. Process 400 may start with unwinding multipleindividual wires from wire rolls or spools in operation 402. In certainembodiments, multiple wires provided in operation 402 may beinterconnected and provided as a woven mesh. However, it would beunderstood by one having ordinary skills in the art that other types ofconductive portions may be used in addition or instead of individualwires. Various examples of wires are described above. The number ofwires depends on a size of the assembly (and a photovoltaic cell) and apitch between the wires. The wires may have different profiles (e.g., around profile or a flat profile).

Process 400 may proceed with extending the wires along the samedirection (i.e., “an unwinding direction”) in operation 404. The wiresmay be substantially parallel during this operation and positioned at apredetermined distance from each other. In other embodiments, wires maybe arranged in other configurations and may even overlap. During thisoperation, the wires may be arranged within substantially the same planeby, for example, applying a tension to the wires. In general, themultiple wires extended in this operation may be characterized as havinga first surface and a second surface regardless of whether thesesurfaces are planar or not. These two surfaces are spaced apart by across-sectional dimension of the wires, such as wire diameters for roundwires or wire thicknesses for flat wires.

FIG. 5 illustrates a schematic view of an apparatus 500 for fabricatingan interconnect wire network assembly, in accordance with certainembodiments. Apparatus 500 includes multiple spools 502 providingmultiple wires 504. Wires 504 remain under tension provided by a rewindroller 508, which is used for the winding of sub-assemblies. The pitchbetween wires 504 may be specific to the positioning of spools 502and/or a guiding mechanism (not shown).

Returning to FIG. 4, process 400 then continues with applying onecarrier film onto the first surface of the wires in operation 406 andapplying another carrier film onto the second surface of the wires inoperation 408. These operations may be performed in parallel or inseries. For example, one carrier film may be initially attached to thewires followed by a separate operation in which another carrier film isattached to the wires. In another example, both films are applied in thesame operation. Edges of the two films can be aligned during this partof the process. Furthermore, in certain embodiments, one or both filmsare applied substantially perpendicular to the unwinding direction.Finally, this part of the process may also involve cutting the carrierfilms, if the films are supplied from continuous rolls. Overall, incertain embodiments, a product of this part of the process is a set ofcontinuous wires with two strips of carrier film attached to theopposite sides of this set of wires. It should be noted that theoperation of applying carrier film strips continues as wires are beingunrolled and fed through the application area.

As shown in FIG. 5, apparatus 500 also includes two carrier film rolls506 a and 506 b, which supply the two films onto the two surfaces of theextended wires 504. A mechanism (not shown) may be employed for grabbingfree ends 507 a and 507 b of the carrier films to extend these filmsfrom rolls 506 a and 506 b and into position with respect to wires 504.A cutting mechanism (not shown) may be employed for cutting the carrierfilms from the rolls 506 a and 506 b along a cutting line 509. Aroll-type or guillotine-type cutter can be used for these purposes.Cutting forms carrier film strips 510 a and 510 b, which are carried bywires 504 to sub-assembly roll 508.

In certain embodiments, applying a carrier film to the wires involvespassing an electric current through at least a portion of the wires thatis in contact with the carrier films. The electrical current heats thisportion of the wires, which may help to adhere the carrier film to thewires. For example, two metal rollers may be put in temporary contactwith wires in the post-application zone 512. A predetermined voltage maybe applied to the rollers at least during the contact period to drivecurrent through the wires and heat the wires. Further, a pressure may beapplied between wires 504 and carrier film strips 510 a and 510 b by,for example, passing a subassembly through nip rollers (e.g., heatedrollers) in the post-application zone.

Returning to FIG. 4, process 400 may proceed with an optional operation410, during which continuous wires with carrier film films may be formedinto a roll as, for example, shown in FIG. 5. This roll is considered tobe a sub-assembly and may be stored prior to further processing, whichinvolves unwinding the toll and cutting the wires to form interconnectwire network assemblies. Process 400 may then proceed with cutting wiresacross their length (e.g., in a direction substantially perpendicular tothe wires) to form the interconnect wire network assembly in operation412. It should be noted that operation 412 may proceed without formingan intermediate subassembly (i.e., without an intermediate optionaloperation 410). A guillotine-type of cutter may be used for thispurpose. Operation 412 may involve cutting only the wires in the areasfree of the carrier films. An example of such an operation is shown inFIG. 6A. Cutting lines 602 are depicted with heavy dashed lines (thindashed lines correspond to the hidden edge of one carrier film strip).Cutting lines 602 pass through wires 504 but not through either one ofcarrier films 510 a and 510 b. In other embodiments, operation 412 mayinvolve cutting both the wires and one or more carrier films. An exampleof such an operation is shown in FIG. 6B where cut lines 604 go throughboth wires and initial carrier film strips 610 a and 610 b. Aftercutting, carrier strip 610 a is divided into new carrier strips 612 aand 614 a, while carrier strip 610 b is divided into new carrier strips612 b and 614 b. New carrier strips 612 a and 612 b together with aportion of wires 606 attached to these strips form an interconnect wirenetwork assembly.

FIG. 7 illustrates a schematic side view of two photovoltaic cells 702and 706 and an interconnect wire network assembly 710 electricallyconnecting these two cells, in accordance with certain embodiments.Assembly 710 includes wires 712 and two carrier films (i.e., top carrierfilm 714 and bottom carrier film 716). In certain embodiments, topcarrier film 714 and bottom carrier film 716 are the same type of films(in terms of thickness and composition). The dimensions of top carrierfilm 714 and bottom carrier film 716 may be the same or different. Topcarrier film 714 and bottom carrier film 716 are shown to overlap in thearea 718. However, other embodiments described above with reference toFIGS. 3A, 3B, and 3C are possible. Photovoltaic cell 702 includes asubstrate 703 and a photovoltaic layer 704 positioned on a front surfaceof a substrate. Similarly, photovoltaic cell 706 includes a substrate707 and a photovoltaic layer 708 positioned on a front surface of asubstrate. A portion of bottom carrier film 716 extends beyond the edgeof photovoltaic cell 702 and over photovoltaic layer 704 of this cell.This feature may be used to prevent short circuits between photovoltaiclayer 704 and substrate 703 and caused by wires 712.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. It should be noted that there are many alternative waysof implementing the processes, systems and apparatus of the presentinvention. Accordingly, the present embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein.

What is claimed is:
 1. A method of fabricating an interconnect wirenetwork assembly comprising: unwinding multiple individual wires fromcorresponding multiple wire rolls; extending the multiple individualwires along an unwinding direction substantially parallel to each otherat a predetermined distance from each other, wherein the multipleindividual wires form a first surface and a second surface, with thefirst surface and the second surface spaced apart by a cross-sectionaldimension of the multiple individual wires; applying a first carrierfilm onto the first surface of the multiple individual wires; andapplying a second carrier film onto the second surface of the multipleindividual wires.
 2. The method of fabricating an interconnect wirenetwork assembly of claim 16, wherein the first carrier film and thesecond carrier film are applied substantially perpendicular to theunwinding direction.
 3. The method of fabricating an interconnect wirenetwork assembly of claim 16, further comprising: forming a roll ofinterconnect wire network subassemblies; unwinding the roll ofinterconnect wire network subassemblies; and cutting the multipleindividual wires substantially perpendicular to the multiple individualwires to form the interconnect wire network assembly.
 4. The method offabricating an interconnect wire network assembly of claim 16, furthercomprising cutting the multiple individual wires substantiallyperpendicular to the multiple individual wires to form the interconnectwire network assembly.
 5. The method of fabricating an interconnect wirenetwork assembly of claim 19, wherein cutting the multiple individualwires comprises cutting the first carrier film or the second carrierfilm.
 6. The method of fabricating an interconnect wire network assemblyof claim 16, wherein applying the first carrier film comprises passingan electric current through a portion of the multiple individual wiresthat is in contact with the first carrier film in order to heat thisportion.